Deep Vein Thrombosis (DVT) is the formation of a thrombus (clot) in a deep vein in a leg. The clot can block blood flow in the leg, or the clot may travel to the lungs causing a potentially fatal pulmonary embolism. The incidence of DVT is particularly high after hip or knee surgery, but may occur whenever patients are immobilized over a period of time. DVT occurrence is known to be high after lower extremity paralysis due to stroke or injury and is also a risk factor in pregnancy, obesity, and other conditions.
Current techniques for avoiding DVT have drawbacks. For example, blood thinning drugs have side effects, elastic stockings and compression devices have limited effectiveness, while compression and exercise devices have limited patient compliance. Active or passive movement of the ankle, alone or in combination with other DVT avoidance techniques, can reduce the incidence of DVT; however there has been no device to assure adequate movement that is acceptable to hospital patients and staff.